The likelihood of a white Christmas is always high -- greater than 75 percent -- in the northern tier of the country and in the mountains of the West. However, the presence of an El Niño and the threat of colder-than-
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The cold air part of the snow recipe has been predicted by computer models that we meteorologists use to help with long-range forecasts. The coupled forecast system, a U.S. government forecasting model, has consistently predicted (since November) that temperatures in the entire eastern half of the country, including the Deep South, will be 1 to 3 degrees colder than normal in December, and it's currently forecasting cold weather for most of the nation for the remainder of the month.
Cold air without storms won't result in snow, of course, but storms combined with cold air might. And storms are more likely than normal where the cold weather is forecast because of a strengthening El Niño. An El Niño is when sea surface temperatures in the equatorial Pacific are warmer than normal, and the moisture and energy from this warm ocean water promotes a storm track across the southern part of the United States. These storms often turn northward along the East Coast.
This weather pattern has already borne fruit (snow, actually) in Southern and Eastern climes. December snow has fallen in El Paso, Dallas and Houston in Texas, as well as in parts of Mississippi, Alabama and Georgia. Snow has also fallen in much of the Northeast. The southern storm track remained active this week, producing the recent coast-to-coast powerhouse of a storm; it originated in California.
So when you mix these ingredients, the current weather pattern might mean fewer people will only "dream" of a white Christmas this year. They'll actually be able to shiver in the cold, spend more time stuck at the airport and drag slush onto Grandma's carpet.
From: http://www.onthesource.com/
